It is common practice in the medical arts to insert various types of flexible catheters or cannulae into blood vessels for purposes of gaining and maintaining vascular access and/or for monitoring of intravascular pressures. One type of intravascular catheter assembly which is particularly suited for percutaneous insertion comprises what is known in the art as the "over-the-needle" (hereinafter "OTN") type. A typical OTN catheter assembly comprises a pliable catheter sheath having a distal end, a proximal end, and a hollow lumen extending axially therebetween A generally rigid introducer needle or other elongate piercing member is disposed axially within the lumen of the catheter such that the beveled distal tip of the needle extends slightly beyond the distal tip of the exteriorly disposed catheter. The protruding distal tip of the needle facilitates puncture of the skin and underlying tissues. After the assembly has been advanced to a desired point (e.g. such that the distal portion of the catheter sheath resides within a blood vessel) the needle is proximally withdrawn and removed from the catheter sheath. The catheter sheath is then allowed to remain within the blood vessel for purposes of continued vascular access and/or transmission of pressure pulses.
One drawback associated with the use of standard OTN-type catheters is that the sharpened distal tip of the introducer needle becomes exposed and unguarded when the needle is withdrawn from the surrounding catheter sheath. Such exposure of the needle tip is known to result in occasional injury (e.g. inadvertant skin puncture or other trauma) to health care workers and others who routinely handle such needles. The occurrence of such inadvertant needle trauma is cause for extreme concern due to the transmissibility and potential seriousness of various blood-borne infections, including hepatitis, Acquired Immune Deficiency Syndrome (AIDS) and others. Thus, the development of new, safer needles and catheter assemblies remains a desirable goal.
In efforts to minimize the occurrence of inadvertant needle induced trauma, a number of modified OTN-type catheter assemblies have incorporated means for shielding or covering the distal tip of the needle after it has been withdrawn from the surrounding catheter. Such modified OTN catheter assemblies are, however, less than optimal in that they are cumbersome, bulky, expensive, and/or require substantial manual manipulation in order to effect the desired covering or shielding of the needle. It is therefore desirable to provide a simple needle tip covering and shielding device which is capable of being attached to the needle in an essentially automatic manner, thereby requiring little or no manual endeavor on the part of the operator.